Koppelaar's work is congenial to a figurative movement in Dutch contemporary painting that evolved during the 1990s in a reaction to the pared-down conceptual art and the too pompous art-theories of that period. Through the years his style evolved into a simpler, straightforward approach.[3] By 1984, he no longer identified himself with any art movement.
Brunt, Ineke & Eisema, Joan (2004), "Gegrepen door het moment - Amsterdam in olieverf" ("Grasped by the moment - Amsterdam in oils"), Stichting de Heeren KeyserISBN 90-808649-3-5
"Amsterdam Urban Landscapes from the Meentwijck Collection" (2003), Auction House Christie's, Amsterdam